In the practice of minimally invasive laparoscopic surgery it is common to make a small incision through the skin and underlying tissue of the patient adjacent the internal surgical site using a Veress needle. These needles include a tubular outer cannula with a sharpened distal end and an inner hollow cylindrical needle which terminates in a blunt end. A spring assembly urges the needle to a position in which the blunt end of the needle is extended beyond the cutting edge of the cannula. When the instrument is pressed against the skin of the patient the blunt end is resisted by the skin so that the outer cannula moves over the blunt end and forms a small incision in the skin and underlying tissue of the patient. When the pressure on the Veress needle is removed, the needle slides forward, leaving a blunt end within the body of the patient, so that the accidental cutting of underlying organs is avoided.
The Veress needle typically includes means for introducing pressurized gas, usually CO2, into the proximal end of the needle so that the gas is passed on into the laparoscopic incision and inflates the body cavity to allow easy access to the surgical site. A trocar which surrounds the cannula and frames the proximal side of the incision may be left in place after the cannula is withdrawn to provide an instrument port with a seal to prevent the escape of the insufflating gas.
After formation of a first incision and insufflation of the body cavity, a second incision, nearby but spaced apart from the first incision, is formed and typically used for insertion of a remote imaging endoscope to allow the surgeon to visualize the internal surgical site. A third incision allows the insertion of an operating instrument.
When the surgery is completed it is necessary to suture one or more of the laparoscopic incisions. Suturing typically involves an instrument that can carry a suture thread into the body cavity and allow the thread to be pulled outwardly through the incision. At the proximal side of the surgical site two ends of the suture are knotted together to secure the incision.
One problem associated with the use of such Veress needle assemblies is determining when the needle has progressed through the wall of the body cavity and its distal end has emerged within the cavity. Additionally, there is a need to determine the location of significant blood vessels in the cavity wall so that the incision made by the needle, as well as the additional incisions necessary to perform the surgery, can be made without cutting these vessels.